package im.actor.crypto.primitives.curve25519;

public class sc_reduce {

//CONVERT #include "sc.h"
//CONVERT #include "long.h"
//CONVERT #include "crypto_uint32.h"
//CONVERT #include "long.h"

public static long load_3(byte[] in, int index)
{
  long result;
  result = ((long) in[index + 0]) & 0xFF;
  result |= (((long) in[index + 1]) << 8) & 0xFF00;
  result |= (((long) in[index + 2]) << 16) & 0xFF0000;
  return result;
}

public static long load_4(byte[] in, int index)
{
  long result;
  result = (((long) in[index + 0]) & 0xFF);
  result |= ((((long) in[index + 1]) << 8) & 0xFF00);
  result |= ((((long) in[index + 2]) << 16) & 0xFF0000);
  result |= ((((long) in[index + 3]) << 24) & 0xFF000000L);
  return result;
}

/*
Input:
  s[0]+256*s[1]+...+256^63*s[63] = s

Output:
  s[0]+256*s[1]+...+256^31*s[31] = s mod l
  where l = 2^252 + 27742317777372353535851937790883648493.
  Overwrites s in place.
*/

public static void sc_reduce(byte[] s)
{
  long s0 = 2097151 & load_3(s, 0);
  long s1 = 2097151 & (load_4(s, 2) >>> 5);
  long s2 = 2097151 & (load_3(s, 5) >>> 2);
  long s3 = 2097151 & (load_4(s, 7) >>> 7);
  long s4 = 2097151 & (load_4(s, 10) >>> 4);
  long s5 = 2097151 & (load_3(s, 13) >>> 1);
  long s6 = 2097151 & (load_4(s, 15) >>> 6);
  long s7 = 2097151 & (load_3(s, 18) >>> 3);
  long s8 = 2097151 & load_3(s, 21);
  long s9 = 2097151 & (load_4(s, 23) >>> 5);
  long s10 = 2097151 & (load_3(s, 26) >>> 2);
  long s11 = 2097151 & (load_4(s, 28) >>> 7);
  long s12 = 2097151 & (load_4(s, 31) >>> 4);
  long s13 = 2097151 & (load_3(s, 34) >>> 1);
  long s14 = 2097151 & (load_4(s, 36) >>> 6);
  long s15 = 2097151 & (load_3(s, 39) >>> 3);
  long s16 = 2097151 & load_3(s, 42);
  long s17 = 2097151 & (load_4(s, 44) >>> 5);
  long s18 = 2097151 & (load_3(s, 47) >>> 2);
  long s19 = 2097151 & (load_4(s, 49) >>> 7);
  long s20 = 2097151 & (load_4(s, 52) >>> 4);
  long s21 = 2097151 & (load_3(s, 55) >>> 1);
  long s22 = 2097151 & (load_4(s, 57) >>> 6);
  long s23 = (load_4(s, 60) >>> 3);
  long carry0;
  long carry1;
  long carry2;
  long carry3;
  long carry4;
  long carry5;
  long carry6;
  long carry7;
  long carry8;
  long carry9;
  long carry10;
  long carry11;
  long carry12;
  long carry13;
  long carry14;
  long carry15;
  long carry16;

  s11 += s23 * 666643;
  s12 += s23 * 470296;
  s13 += s23 * 654183;
  s14 -= s23 * 997805;
  s15 += s23 * 136657;
  s16 -= s23 * 683901;
  s23 = 0;

  s10 += s22 * 666643;
  s11 += s22 * 470296;
  s12 += s22 * 654183;
  s13 -= s22 * 997805;
  s14 += s22 * 136657;
  s15 -= s22 * 683901;
  s22 = 0;

  s9 += s21 * 666643;
  s10 += s21 * 470296;
  s11 += s21 * 654183;
  s12 -= s21 * 997805;
  s13 += s21 * 136657;
  s14 -= s21 * 683901;
  s21 = 0;

  s8 += s20 * 666643;
  s9 += s20 * 470296;
  s10 += s20 * 654183;
  s11 -= s20 * 997805;
  s12 += s20 * 136657;
  s13 -= s20 * 683901;
  s20 = 0;

  s7 += s19 * 666643;
  s8 += s19 * 470296;
  s9 += s19 * 654183;
  s10 -= s19 * 997805;
  s11 += s19 * 136657;
  s12 -= s19 * 683901;
  s19 = 0;

  s6 += s18 * 666643;
  s7 += s18 * 470296;
  s8 += s18 * 654183;
  s9 -= s18 * 997805;
  s10 += s18 * 136657;
  s11 -= s18 * 683901;
  s18 = 0;

  carry6 = (s6 + (1<<20)) >> 21; s7 += carry6; s6 -= carry6 << 21;
  carry8 = (s8 + (1<<20)) >> 21; s9 += carry8; s8 -= carry8 << 21;
  carry10 = (s10 + (1<<20)) >> 21; s11 += carry10; s10 -= carry10 << 21;
  carry12 = (s12 + (1<<20)) >> 21; s13 += carry12; s12 -= carry12 << 21;
  carry14 = (s14 + (1<<20)) >> 21; s15 += carry14; s14 -= carry14 << 21;
  carry16 = (s16 + (1<<20)) >> 21; s17 += carry16; s16 -= carry16 << 21;

  carry7 = (s7 + (1<<20)) >> 21; s8 += carry7; s7 -= carry7 << 21;
  carry9 = (s9 + (1<<20)) >> 21; s10 += carry9; s9 -= carry9 << 21;
  carry11 = (s11 + (1<<20)) >> 21; s12 += carry11; s11 -= carry11 << 21;
  carry13 = (s13 + (1<<20)) >> 21; s14 += carry13; s13 -= carry13 << 21;
  carry15 = (s15 + (1<<20)) >> 21; s16 += carry15; s15 -= carry15 << 21;

  s5 += s17 * 666643;
  s6 += s17 * 470296;
  s7 += s17 * 654183;
  s8 -= s17 * 997805;
  s9 += s17 * 136657;
  s10 -= s17 * 683901;
  s17 = 0;

  s4 += s16 * 666643;
  s5 += s16 * 470296;
  s6 += s16 * 654183;
  s7 -= s16 * 997805;
  s8 += s16 * 136657;
  s9 -= s16 * 683901;
  s16 = 0;

  s3 += s15 * 666643;
  s4 += s15 * 470296;
  s5 += s15 * 654183;
  s6 -= s15 * 997805;
  s7 += s15 * 136657;
  s8 -= s15 * 683901;
  s15 = 0;

  s2 += s14 * 666643;
  s3 += s14 * 470296;
  s4 += s14 * 654183;
  s5 -= s14 * 997805;
  s6 += s14 * 136657;
  s7 -= s14 * 683901;
  s14 = 0;

  s1 += s13 * 666643;
  s2 += s13 * 470296;
  s3 += s13 * 654183;
  s4 -= s13 * 997805;
  s5 += s13 * 136657;
  s6 -= s13 * 683901;
  s13 = 0;

  s0 += s12 * 666643;
  s1 += s12 * 470296;
  s2 += s12 * 654183;
  s3 -= s12 * 997805;
  s4 += s12 * 136657;
  s5 -= s12 * 683901;
  s12 = 0;

  carry0 = (s0 + (1<<20)) >> 21; s1 += carry0; s0 -= carry0 << 21;
  carry2 = (s2 + (1<<20)) >> 21; s3 += carry2; s2 -= carry2 << 21;
  carry4 = (s4 + (1<<20)) >> 21; s5 += carry4; s4 -= carry4 << 21;
  carry6 = (s6 + (1<<20)) >> 21; s7 += carry6; s6 -= carry6 << 21;
  carry8 = (s8 + (1<<20)) >> 21; s9 += carry8; s8 -= carry8 << 21;
  carry10 = (s10 + (1<<20)) >> 21; s11 += carry10; s10 -= carry10 << 21;

  carry1 = (s1 + (1<<20)) >> 21; s2 += carry1; s1 -= carry1 << 21;
  carry3 = (s3 + (1<<20)) >> 21; s4 += carry3; s3 -= carry3 << 21;
  carry5 = (s5 + (1<<20)) >> 21; s6 += carry5; s5 -= carry5 << 21;
  carry7 = (s7 + (1<<20)) >> 21; s8 += carry7; s7 -= carry7 << 21;
  carry9 = (s9 + (1<<20)) >> 21; s10 += carry9; s9 -= carry9 << 21;
  carry11 = (s11 + (1<<20)) >> 21; s12 += carry11; s11 -= carry11 << 21;

  s0 += s12 * 666643;
  s1 += s12 * 470296;
  s2 += s12 * 654183;
  s3 -= s12 * 997805;
  s4 += s12 * 136657;
  s5 -= s12 * 683901;
  s12 = 0;

  carry0 = s0 >> 21; s1 += carry0; s0 -= carry0 << 21;
  carry1 = s1 >> 21; s2 += carry1; s1 -= carry1 << 21;
  carry2 = s2 >> 21; s3 += carry2; s2 -= carry2 << 21;
  carry3 = s3 >> 21; s4 += carry3; s3 -= carry3 << 21;
  carry4 = s4 >> 21; s5 += carry4; s4 -= carry4 << 21;
  carry5 = s5 >> 21; s6 += carry5; s5 -= carry5 << 21;
  carry6 = s6 >> 21; s7 += carry6; s6 -= carry6 << 21;
  carry7 = s7 >> 21; s8 += carry7; s7 -= carry7 << 21;
  carry8 = s8 >> 21; s9 += carry8; s8 -= carry8 << 21;
  carry9 = s9 >> 21; s10 += carry9; s9 -= carry9 << 21;
  carry10 = s10 >> 21; s11 += carry10; s10 -= carry10 << 21;
  carry11 = s11 >> 21; s12 += carry11; s11 -= carry11 << 21;

  s0 += s12 * 666643;
  s1 += s12 * 470296;
  s2 += s12 * 654183;
  s3 -= s12 * 997805;
  s4 += s12 * 136657;
  s5 -= s12 * 683901;
  s12 = 0;

  carry0 = s0 >> 21; s1 += carry0; s0 -= carry0 << 21;
  carry1 = s1 >> 21; s2 += carry1; s1 -= carry1 << 21;
  carry2 = s2 >> 21; s3 += carry2; s2 -= carry2 << 21;
  carry3 = s3 >> 21; s4 += carry3; s3 -= carry3 << 21;
  carry4 = s4 >> 21; s5 += carry4; s4 -= carry4 << 21;
  carry5 = s5 >> 21; s6 += carry5; s5 -= carry5 << 21;
  carry6 = s6 >> 21; s7 += carry6; s6 -= carry6 << 21;
  carry7 = s7 >> 21; s8 += carry7; s7 -= carry7 << 21;
  carry8 = s8 >> 21; s9 += carry8; s8 -= carry8 << 21;
  carry9 = s9 >> 21; s10 += carry9; s9 -= carry9 << 21;
  carry10 = s10 >> 21; s11 += carry10; s10 -= carry10 << 21;

  s[0] = (byte)(s0 >> 0);
  s[1] = (byte)(s0 >> 8);
  s[2] = (byte)((s0 >> 16) | (s1 << 5));
  s[3] = (byte)(s1 >> 3);
  s[4] = (byte)(s1 >> 11);
  s[5] = (byte)((s1 >> 19) | (s2 << 2));
  s[6] = (byte)(s2 >> 6);
  s[7] = (byte)((s2 >> 14) | (s3 << 7));
  s[8] = (byte)(s3 >> 1);
  s[9] = (byte)(s3 >> 9);
  s[10] = (byte)((s3 >> 17) | (s4 << 4));
  s[11] = (byte)(s4 >> 4);
  s[12] = (byte)(s4 >> 12);
  s[13] = (byte)((s4 >> 20) | (s5 << 1));
  s[14] = (byte)(s5 >> 7);
  s[15] = (byte)((s5 >> 15) | (s6 << 6));
  s[16] = (byte)(s6 >> 2);
  s[17] = (byte)(s6 >> 10);
  s[18] = (byte)((s6 >> 18) | (s7 << 3));
  s[19] = (byte)(s7 >> 5);
  s[20] = (byte)(s7 >> 13);
  s[21] = (byte)(s8 >> 0);
  s[22] = (byte)(s8 >> 8);
  s[23] = (byte)((s8 >> 16) | (s9 << 5));
  s[24] = (byte)(s9 >> 3);
  s[25] = (byte)(s9 >> 11);
  s[26] = (byte)((s9 >> 19) | (s10 << 2));
  s[27] = (byte)(s10 >> 6);
  s[28] = (byte)((s10 >> 14) | (s11 << 7));
  s[29] = (byte)(s11 >> 1);
  s[30] = (byte)(s11 >> 9);
  s[31] = (byte)(s11 >> 17);
}


}
